1. Field of the Invention
The present invention relates to a photoactive compound having a novel structure and a photosensitive resin composition comprising the same and, more particularly, to a photoactive compound, having high absorptivity for UV light, excellent sensitivity and high-temperature process characteristics, and excellent compatibility in a photosensitive resin composition, and a photosensitive resin composition comprising the photoactive compound.
2. Discussion of the Related Art
A photoactive compound is substance which is decomposed by absorbed light and formed to generate atoms or molecules having activity chemically. The photoactive compound is being widely used in photosensitive resin composition, and so on. Substance having the chemical activity may include, for example, acids, bases, and radicals. In particular, a photoactive compound from which the radicals, from among the acids, bases, and radicals, are generated may be used with acryl groups, generating polymerization along with the radicals, in order to improve the strength of a coated film.
Meanwhile, a photosensitive resin composition may be used to form patterns by coating the photosensitive resin composition on a substrate to form a conductive film, exposing specific portions of the conductive film to light using a photomask, etc., and then developing and removing the non-exposure portions of the conductive film. The photosensitive resin composition is being used in photocurable ink, photosensitive printing sheets, various photoresists, color filter photoresists for LCDs, photoresists for resin black matrices, and transparent photosensitizers because it can be radiated by light, can be polymerized, and hardened.
Furthermore, with the high quality and diversification of LCDs, the photosensitive resin composition is being fabricated to constitute liquid crystal display devices, such as TV and monitors, in addition to display devices for use in the existing notebook computers and mobiles. There is an increasing demand for photosensitive resin compositions, having a fast response to light and mechanically excellent physical properties, in order to improve productivity and durability.
In particular, in the case where patterns are formed by a photolithography method and an insulating protection film is formed through blanket exposure, a characteristic having a fast response to light (that is, photosensitivity) is becoming an important factor. Furthermore, column spacers, playing the role of supports, or an overcoat and a passivation film, playing the role of a protection film, must have excellent mechanical physical properties so that liquid crystal display devices exhibit their original performance without being broken by external shock.
The above problems can be solved by using a photopolymerization initiator with excellent photosensitivity. If the photopolymerization initiator having excellent photosensitivity is used, there are advantages in that a pollution source due to liquid crystals can be reduced, a residual film thickness of patterns can be increased, and other available raw materials when a composition is fabricated can be widely selected because sufficient sensitivity can be implemented even by a small amount of a photopolymerization initiator.
In general, the photopolymerization initiators used in the photosensitive resin composition includes some known kinds, such as acetophenone derivatives, benzophenone derivatives, non-imidazole derivatives, acylphosphine oxide derivatives, triazine derivatives, and oxime ester derivatives. From among them, the oxime ester derivatives are advantageous in that they rarely wear color because they absorb ultraviolet rays, have high radical generation efficiency, and have excellent stability within the composition.
α-oxooxime derivatives, a combined use of thioxanthone and an oxime ester compound, oxime ester in which p-dialkylaminobenzene is used as a synergist, photoinitiators using β-aminooxime, oxime ether photoinitiator comprising ethylene-based unsaturated groups in a molecular structure, and the like have been developed as the photoinitiator of an oxime ester structure. However, the early developed oxime derivative compounds are problematic in that they have low photoinitiation efficiency and they are inefficient in absorbing UV light when they have a good color characteristic.
There have been developments for improving the photoinitiation efficiency, but the developments do not sufficiently achieve a reduction in the turn around time. In particular, the developments are problematic in that they form fine patterns because they do not sufficiently satisfy the degree of cure of a thick film, having a high concentration of pigments and having a coated film of 2.5 μm or higher in thickness. Furthermore, patterns formed by the developments do not satisfy critical dimension (CD) or mechanical strength required for products.
Irgacure OXE 01 or Irgacure OXE 02 (recently commercialized oximeester-based photoinitiators) by CIBA SPECIALTY CHEMICAL CORP. has significantly improved sensitivity, but is disadvantageous in that it may not be used to such a degree that it can exhibit sufficient sensitivity from an economical point of view because it is very expensive and in that the initiator itself has low storage stability.
Accordingly, there is a need for the development of a photoactive compound (that is, a photopolymerization initiator), capable of efficiently absorbing UV light even with a small amount and having excellent sensitivity, high-temperature process characteristic, and solubility, and a photosensitive resin composition comprising the photoactive compound.